Regarding the bug in FreeBSD kernel driver(s)

[John Baldwin]

On 8/13/19 1:14 PM, Hans Petter Selasky wrote:
> On 2019-08-13 22:08, Ian Lepore wrote:
>> So once a device is attached the first time, its usb ivars are wiped
>> out.  That code was surely written in a time before the devctl stuff
>> was added to allow disabling/enabling a device on the fly.  I'm not
>> sure whether it will be easy to keep the ivar data around, but if so, I
>> think that would be the right fix.
>>
>> The NULL pointer checks in the patches will prevent a kernel panic, but
>> don't really make devctl enable work properly.  Speaking of devctl, you
>> don't need a program to test this, you can do it from the command line:
>>
>>     devctl disable uhub2
>>     devctl enable uhub2
>>     <panic happens here>
> 
> Hi,
> 
> USB drivers are not supposed to be managed outside the USB enumeration 
> thread. Using devctl on USB driver is not supported. Only usbconfig is 
> allowed to attach/detach USB devices.
> 
> Should we perhaps teach devctl to not touch USB devices?

I think fixing USB to not break by preserving ivars is probably a better
long-term solution.  ivars are not supposed to be freed and rebuilt but
should exist for the lifetime of a device_t.

-- 
John Baldwin